For Tropical Storm Isaac, it's too early to tell strength, landing spot

08 24, 2012 by The Times-Picayune

As Tropical Storm Isaac cuts through the Caribbean Sea with its long-term aim set on the northern Gulf of Mexico, somewhere between Louisiana and the Florida Panhandle, state and local emergency managers already are scrambling to get state residents prepared for a worst-case scenario. "Our message would be for residents to monitor the media and their local officials and also to begin reviewing their plans -- to have a game plan, as we've been talking about all year," said Kevin Davis, director of the Governor's Office of Homeland Security and Emergency Preparedness.

With lower Plaquemines Parish and outermost St. Bernard Parish already lying within the National Hurricane Center's five-day forecast error bubble, the state already is within its 120-hour evacuation planning window, Davis said, although an evacuation is not yet anticipated.

At 10 p.m. Thursday, the center predicted that by 2 p.m. Tuesday, Isaac would be a Category 1 hurricane with top winds of 85 mph, and it would be just south of Appalachicola, Fla.

"But beyond two or three days, our forecast's uncertainty increases quite a bit," said Dan Brown, senior hurricane specialist. He said a western finger of a ridge of high pressure that's been steering Isaac west is expected to weaken in a few days, allowing the storm to turn more northwest. A trough of low pressure moving east across the United States could pull the storm more to the east, but he said forecasters don't think that's likely.

Also problematical is predicting the intensity of the storm.

"It looks like the conditions are favorable for continued strengthening over the Caribbean Sea, but it's likely to interact with land" as it moves over a long segment of Cuba, Brown said.

When it moves into the Straits of Florida and the Gulf, however, it will pass over 86-degree water that's likely to increase its intensity.

Plans hinge on storm size

Isaac's intensity and size, in addition to its location, will determine whether evacuations will be required for any parts of Louisiana. The state generally evacuates only areas outside the hurricane levee system for storms of Category 2 intensity, with top winds of 110 mph, or below, Davis said. Local elected officials make those decisions, in coordination with the state.

For Category 3 and stronger storms, with sustained winds of 111 mph or greater, a Phase I evacuation focusing on areas outside the levee system, including locations south of the Intracoastal Waterway, would begin 50 hours before tropical storm force winds, 39 mph and greater, are forecast to reach the shoreline.

Phase II begins 40 hours before tropical storm winds hit the shore and includes areas inside the levees on the West Bank, south of the Mississippi River.

Phase III begins 30 hours before tropical storm-force winds hit the shore, and includes New Orleans area neighborhoods on the east bank inside the levee system. During this phase, state and local officials also are likely to institute a contraflow plan, with all traffic directed east or west of New Orleans along all lanes of interstate highways in those directions.

Davis said the state also would implement plans for moving residents without transportation to shelters outside the New Orleans area, as needed, as part of the evacuation program for the larger storms. The evacuation plan also will transport pets in air-conditioned vehicles to state-run animal shelters.

Destination unknown

All of the evacuation plans, however, depend on forecasting Isaac's eventual path across the Gulf of Mexico, which was anything but certain on Thursday night.

In his 5 p.m. discussion message, Jack Beven, also a senior hurricane specialist, warned that while several computer models have shifted the forecast path westward during the past few days, there are several key models that still show it moving along a line closer to Florida's west coast, which could prove a threat to Tampa during next week's Republican National Convention.

At least one model also shows it moving ashore just west of the Mississippi River next Thursday.

The uncertainty is partly the result of Isaac's slowly developing core, which still contained several rotating batches of clouds Thursday afternoon. Until there's a single center of circulation, it's difficult for the models to determine a starting point, and thus an ending point for their forecast runs.

The uncertainty just adds to the need to be prepared, emergency officials said.

Getting ducks in a row

"People should be checking to see if their personal plans are in place, or asking about how to develop those plans," said Kay Wilkins, chief executive officer of the southeast Louisiana chapter of the American Red Cross. "It's time to make sure you still have that disaster kit, that the batteries are replaced, making sure you've got enough water -- a gallon per person per day for a five- or seven-day period.

"And they should be making sure they have a plan for people and pets who can't take care of themselves," Wilkins said.

For toddlers, that means making sure there's enough special formula, toys or blankets for several days of an evacuation, she said. For seniors and those with special needs, it means making sure medication and special medical equipment are on hand and that their planned evacuation location will have an electrical supply, if needed.

The Red Cross recently unveiled a smartphone app, available for iPhones and Google-based devices, that includes helpful hints and the ability to alert individuals to ZIP code-based hurricane, tropical storm, tornado and flood warnings and watches. Similar information is available through the organization's national website.

The state also has apps for family emergency planning available through its emergency planning website.